WASHINGTON -- Consumer prices rose a moderate 0.2% in April, but the increase was the largest in six months and it renewed speculation on Wall Street that the Federal Reserve may soon raise interest rates.

The bump came after the Labor Department's consumer price index showed that prices were flat in March. Meanwhile, the core inflation rate, which excludes volatile food and energy prices, rose a seasonally adjusted 0.3% in April, from an increase of 0.1% in March. But overall, inflation remains contained: The annual...